title: Prevalence of β-lactamases and 16S rRNA methylase genes amongst clinical Klebsiella pneumoniae isolates carrying plasmid-mediated quinolone resistance determinants.
abstract: To characterise the prevalence of β-lactamases and 16S rRNA methylase genes amongst clinical Klebsiella pneumoniae isolates carrying plasmid-mediated quinolone resistance (PMQR) determinants in China, 59 non-duplicate K. pneumoniae isolates harbouring at least one PMQR gene were screened for common β-lactamases and 16S rRNA methylases genes. The genetic relatedness of the isolates was analysed by pulsed-field gel electrophoresis (PFGE). Most of PMQR gene-positive isolates carried no substitutions within the quinolone resistance-determining regions (QRDRs) or single point mutation in GyrA or ParC. Over one-half (52.5%) of the isolates exhibited decreased susceptibility to ciprofloxacin [minimum inhibitory concentration (MIC)=0.5-2 μg/mL] or low-level resistance to ciprofloxacin (MIC=4-8 μg/mL). qnr, aac(6')-Ib-cr and qepA were positive in 52 (88.1%), 16 (27.1%) and 3 (5.1%) isolates, respectively. The identified genes for β-lactamases were distributed as follows: bla(TEM), 50.8%; bla(SHV), 91.5%; bla(CTX-M), 55.9%; bla(DHA), 59.3%; and bla(OXA-1), 22.1%. armA and rmtB were detected in 16.9% and 3.4% of isolates, respectively. All qnrB were detected in DHA-producing K. pneumoniae. Approximately 81.3%, 68.8% and 43.8% of aac(6')-Ib-cr carrying isolates produced OXA-1, DHA and ArmA, respectively. In conclusion, owing to few QRDR substitutions, most of the PMQR gene-carrying K. pneumoniae isolates exhibited low-level resistance to fluoroquinolones. qnr appears to be the predominant PMQR gene and it presented a significant correlation with bla(SHV), bla(CTX-M) and bla(DHA), whereas aac(6')-Ib-cr exhibited a close relationship with bla(OXA-1), bla(DHA) and armA. qepA was rarely detected in this study.
authors.affiliation: Department of Microbiology, Chinese PLA General Hospital, 28# Fuxing Road, Beijing 100853, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Luo
authors.forename: Jiyong
authors.initials: J
authors.lastname: Yang
authors.forename: Youjiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Liyan
authors.initials: L
authors.lastname: Ye
authors.forename: Leili
authors.initials: L
authors.lastname: Wang
authors.forename: Ling
authors.initials: L
authors.lastname: Guo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D017931:DNA Primers; D004352:Drug Resistance, Microbial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D015363:Quinolones / Q000494:pharmacology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers; D015363:Quinolones; D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; D001618:beta-Lactamases